1. Field of the Invention
This invention relates to end turn support arrangements for dynamoelectric machines.
2. Description of the Prior Art
In the dynamoelectric machine art there continues to be a need for improving the support arrangement for the end turn portions of the winding coils extending from the ends of the stators of dynamoelectric machines such as large turbine generators. Manifestly, the stresses imposed during operation, particularly those caused by vibration, result in wear of coil insulation and fatigue cracking of series and copper strand phase connections. Many proposals have been made in the past in an effort to solve this long standing problem and examples of prior art arragements are illustrated in U.S. Pat. Nos. 3,949,256; 3,949,257; 4,379,243; and 4,488,079, the entireties of the disclosures of which are hereby specifically incorporated herein by reference. Other proposals have included packing the entire end turn area with a thixotropic, curable potting resin such as an epoxy, a polyester or a polyurethane material.
Among the problems encountered through the use of resin fillers is that fillers, and in particular the epoxies, which have the best mechanical properties generally have a coefficient of thermal expansion which appears to be approximately 4 times as great as the apparent coefficient of thermal expansion of the end turns themselves. Although such coefficients are difficult to calculate with any mathematical exactitude, the general result of a significant mismatch between the coefficients of the filler material and of the end turn windings often is a debonding of the resin filler from the windings.
Another problem encountered when using potting resin type materials is that the curing reaction is generally highly exothermic, and when the volume of the curing material is too great, hot spots sufficient to actually destroy the resin may develop internallly.
The present invention is aimed at the provision of novel support arrangements including filler materials which solve the problems encountered in using prior art resin fillers.